The temperature of the refrigerator is not constant

Hi @ahmadehteram

What is the model number of the refrigerator?

-10°C for 1 hour is a little long but it seems like it is performing an automatic defrost cycle, which is normal.

Usually the defrost cycle lasts for about 20-25 minutes

Normally a defrost cycle is performed once every 10-12 hours of elapsed time or every 8-10 hours of cumulative compressor run time. It depends on what method the manufacturer has decided to use in your model.

When a defrost cycle occurs, the compressor and evaporator fans are both turned off and the temperature in the freezer is allowed to rise to start melting the accumulated ice from the evaporator. A defrost heater under the evaporator unit is also turned on to speed up the process.

When the defrost cycle has ended (timed event controlled by either the control board or a separate defrost timer) the heater is turned off and the compressor and evaporator fan are both turned on again to drive the temps back to within the normal preset operating range.